JP2007-517369A discloses a fuel cell system in which high-pressure anode gas is repeatedly supplied and stopped, whereby a pressure of the anode gas pulsates. In such a fuel cell system, the high-pressure anode gas is supplied. This causes impurities staying in a reaction flow passage to be pushed into a buffer tank, whereby an anode gas concentration in the reaction flow passage is increased and power is generated. Subsequently, by stopping the supply of the anode gas and continuing power generation, the anode gas is consumed and a pressure in the reaction flow passage decreases. Associated with this, the anode gas discharged to the buffer tank reversely flows to be consumed for power generation reaction. When impurities reversely flowing together with the anode gas and those cross-leaking from a cathode side increase, the high-pressure anode gas is supplied again.
By repeating such operations, the anode gas concentration in the reaction flow passage is maintained to continue power generation.
Related inventions known to the public through publications are also described in JP2008-97966A and JP2007-149630A.